Abstract

The rheological characteristics of extrudates from corn semolina and mixture of corn semolina and tapioca flour were examined by rotational viscometer "Brookfield” RV-DV II + Pro. A non-linear relationship between the shear stress and the shear rate was established. The model of Ostwald–de Waele was applied and flow and consistency indexes were calculated and used to analyse the rheological behavior of the tested samples. The change of the effective viscosity as a function of the shear rate, depending on the moisture of the mixture, temperature and tapioca content was studied. In this study the addition of tapioca flour to corn semolina increased the viscosity of the extrudates by 60 %. The results suggest that tapioca flour influence the rheological properties of food products and can be used as a thickening additive to various kinds of food.

Key words: Corn, Rheology, Tapioca, Viscosity, Extrudates.